With the progress in communication systems, consumers such as companies and individuals have used a wide variety of wireless terminals.
Current mobile communication systems affiliated with Third Generation Partnership Project (3GPP), for example, Long Term Evolution (LTE), LTE-Advanced (LTE-A), and the like, require a high-speed and high-capacity communication system capable of transmitting and receiving various data, such as image and music data, program data, and the like, beyond providing voice-oriented services.
For a high-speed and high-capacity communication system, technology capable of increasing the capacity of a user equipment by using a small cell is required.
Also, in an environment where a macro cell base station is connected to a small cell base station via a non-ideal backhaul, it is required to establish a small cell and a radio bearer in order to allow a user equipment to transmit user plane data through the small cell.
In this case, the macro cell base station and the user equipment are required to perform establishment procedures, such as addition/modification of a small cell, addition/modification of a radio bearer which is to be configured in a base station providing a small cell, and the like.